Cleaning - Active baths for engine parts

If cleaned in the wrong bath, the component has to be scrapp

Before the specialists in non-destructive material testing can start looking for the first material weaknesses and defects on and just below the surface and also inside a component, all dirt and deposits have to be removed. The methods used to clean the engine parts are specifically tailored to the substances out of which they are constructed. Thus, materials like titanium, nickel-base, cobalt, magnesium and steel alloys and also aluminum all require a cleaning regime specifically geared towards that particular material. Tanks containing both alkaline and acidic cleaning agents are available in Lufthansa Technik's engine shop. Solution temperature and cleaning duration are important parameters and are computer-controlled in the fully automated plant. Components made of the same material are stowed in baskets with a capacity of around 1.5 cubic meters as a single batch. Careful notes are taken as to which technician has introduced which batch to which cleaning solution, as the wrong fluid normally abruptly terminates the useful life of parts which in most cases will have cost many thousands of euros.

The batches of parts all constructed from the same material are then bathed at a temperature of around 90 degrees Celsius. Ultrasonic waves are employed to increase cleaning efficacy in the case of stubborn dirt. Layers of scale are then shotblasted in chambers with wet aluminum oxide abrasives. Having emerged from the active baths, the cleaning baskets are conveyed to two rinsing baths containing deionized (fully demineralized) water, where the fluid cascades down from one level to the next, the last bath containing completely pure water. A sensor in the rinsing tanks continually measures the guide values. As soon as the accumulation of minerals causes the salt content to rise above the acceptable limit, fresh deionized water is introduced. Reverse osmosis is employed to filter the used water in Lufthansa Technik's central industrial water treatment plant, following which it is reintroduced into the engine cleaning process.

All 20 cleaning tanks are sealed, and an extraction system draws off the vapors. These are cleaned in a gas scrubber, and only then is the purified air released outside. Once a month a sample is taken from the baths to measure the concentration and, where necessary, adjust the composition. Or, to use the technical jargon, "the cleaning medium is regenerated" – as a clean surface is the basic precondition for the ensuing tests.